Sulfur-containing phenolic compounds



United States Patent Ofi ice 3 ,Z50,71Z Patented May 10, 1966SULFUR-CONTAINING PHENOLIC COMPOUNDS Thomas H., Cotfield, Farmington,Mich., assignor to Ethyl Corporation, New York, N.Y., a corporation ofVirginia No Drawing. Original application July 24, 1959, Ser. No.

829,232. Divided and this applicationJuly 23, 1962,

Ser. No. 211,829

The portion of the term of the patent subsequent to Oct. 22, 1979, hasbeen disclaimed 6 Claims. (Cl. 25248.2)

This application is a division of application Serial No. 829,232, filedJuly 24, 1959, and now abandoned, which 'in turn is acontinuation-in-part of applications Serial No. 720,825, filed March 12,1958, and now U.S. Patent No. 3,057,926 and Serial No. 779,068, filedDecember 9, 1958, and now U.S. Patent No. 3,069,384.

This invention deals with a novel class of organic compounds which areeminently suited to the protection of synthetic hydrocarbon polymers andother organic material from oxidative deterioration.

It is an object of this invention to provide a novel class of phenoliccompounds. A further object is to provide a special class of phenolicsulfur compounds which have outstanding antioxidant properties when usedin small amounts in certain synthetic hydrocarbon polymers and otherorganic material. A further object is to provide as a new composition ofmatter, synthetic hydrocarbon polymers which are stabilized by thephenolic sulfur compounds herein disclosed. A specific o-bject of thisinvention is to provide polyethylene which possesses outstandingoxidative stability.

The objects of this invention are accomplished by providing a compoundhaving the formula:

R R l HO S.@ H RI I'V wherein R is an alkyl group branched on the alphacarbon atom and having from 3 to 4 carbon atoms inclusive and R' is amember of the class consisting of alkoxy groups having from 1 to 4carbon atoms and alkyl groups branched on the alpha carbon atoms havingfrom 3 to 4 carbon atoms, and x is an integer from 2 to 3 inclusive.

These compounds are extremely effective antioxidants in a very widerange of organic material. They are superior to closely relatedcompounds having different configurations of substituents on thephenolic nucleus. They are unexpectedly more effective than theserelated compounds and those which contain only a single sulfur atombetween the phenolic nuclei. In addition, the compounds of thisinvention do not have the inherent disadvantages of other knownantioxidants. Thus, the compounds of this invention do not corrode metalsurfaces norcause undesirable color in the substrate which they protectagainst oxidation. Furthermore, the compounds of this invention areeffective antioxidants under service conditions in which otherantioxidants are prone to become ineffective.

The compounds of this invention include: 4,4'-dithiobis (2,6-di-tert-butylphenol) 4,4'-trithiobis- (2-methoxy-6- isopropylphenol),4,4'-dithiobis-(2-isopropyl-6-sec-butylphenol), 4,4-dithiobis-(2,6-diisopropylphenol), 4,4'-dithiobis-(2-ethoxy-6-tert-butylphenol)4,4 trithiobis (2- rnethoxy-6-sec-butylphenol),4,4'-dithiobis-(Z-n-propoxy- 6-tert-butylphenol), 4,4'-trithiobis-(2-secbutyl-6-tert-butylphenol), and the like.

The alkyl radical represented by R in the above formula includes theisopropyl group, the tert-butyl group and the secondary butyl group. Thenovel compounds containing these groups are readily prepared and areextremely effective antioxidants as will be described in more detailbelow. Those compounds in which R is a tert-butyl or isopropyl group arepreferred as it is found that they are outstanding antioxidants.

The alkoxy groups which may constitute the group R' in the aboveformulas are those lower alkoxy groups having from 1 to 4 carbon atomsand thus include the methoxy, ethoxy, propoxy, isopropoxy, butoxy,sec-butoxy, tert-butoxy and isobutoxy. Of these the methoxy group ispreferred as compounds containing this group are found to be more easilyprepared;

The compounds of this invention have been found to be outstandingantioxidants. Thus, an embodiment of this invention is a new compositionof matter which comprises organic material hormally tending to undergooxidative deterioration in the presence of air, oxygen or ozone,containing a small antioxidant quantity, up to 5 percent, of a compoundhaving the formula:

wherein R is an alkyl group branched on the alpha carbon atom havingfrom 3 to 4 carbon atoms inclusive, R is selected from alkoxy groups ofl to 4 carbon atoms and alkyl groups branched on the alpha carbon atomhaving from 3 to 4 carbon atoms, and-x is an integer from 2 to 3. Thequantity of antioxidant employed will vary from a small quantity, suchas 0.001 percent by weight to a larger amountfrom 3 to 5 percent,depending on the inherent stability of the material to be protected.

The compounds of this invention find important utility as antioxidantsin a wide variety of oxygen sensitive ma: terials. Thus, liquidhydrocarbon fuels such as gasoline, kerosene and fuel oil are found topossess greatly increased storage stability by .the use of anantioxidant of this invention. Likewise, liquid hydrocarbon fuels suchas gasoline which contain organometallic additives such astetraethyllead, as well as other organometallic compounds which are usedas fuel additives, attain appreciably increased oxidative stability bythe practice of this invention. In addition, lubricating oils andfunctional fluids, both those derived from naturally occurringhydrocarbons and those synthetically prepared, are greatly enhanced bythe practice of this invention. The addition of small quantities of thecompounds of 'this invention to such materials as turbine, hydraulic,transformer and other highly refined industrial oils; waxes; soaps andgreases; plastics; organometallic compositions such as tetraethylleadand tetraethyllead antiknock fluids; elastomers, including naturalrubber; crankcase lubricating oils; lubricating greases; and the like,greatly increase their resistance to deterioration in the presence ofair, oxygen or ozone.

The compounds of this invention are also very effective antioxidants forhigh molecular weight unsaturated hydrocarbon polymers, such aspolybutadiene, methyl rubber, polybutene rubber, natural rubber, butylrubber, GR-S rubber, GR-N rubber, piperylene rubber, dimethyl butadienerubber and the like.

The compounds of this invention are also useful in protecting petroleumwax-paraflin wax and micro-crystalline wax-against oxidativedeterioration. The compounds of this invention also find use in thestabilization of edible fats and oils of animal or vegetable originwhich tend to become rancid especially during long periods of storagebecause of oxidative deterioration. Typical representatives of theseedible fats and oils are linseed oil, cod liver oil, castor oil, soybeanoil, rape- In the various embodiments of this invention the sta-'bilizer is used in small amounts, generally ranging from about 0.001 toabout 5.0 percent.

As used in the description and claims, the term rubber is employed in ageneric sense to define a high molecular weight plastic material whichpossesses high extensibility under load coupled with the property offorcibly retracting to approximately its original size and shape afterthe load is removed. It is preferable that the rubber be asulfur-vuloanizable rubber, such as India rubber, reclaimed rubber,balata, gutta-percha, rubbery conjugated diene polymers and copolymersexemplified by the butadiene-styrene (GR-S) and butadieneacrylonitrile(GR-N or Paracril) rubbers and the like, although the invention isapplicable to the stabilization of any rubbery, high molecular weightorganic material which is normally susceptible to deterioration in thepresence of oxygen, air, or ozone. The nature of these rubbers is wellknown to those skilled in the art.

Among the definite advantages provided by this invention is that thepresent rubber compositions possess unusually great resistance againstoxidative deterioration. Moreover, these compositions exhibit excellentnonstaining and non-discoloration characteristics. Furthermore, thenovel thiobisphenol stabilizer is relatively inexpensive and easilyprepared, and possesses the highly beneficial property of lowvolatility. As is well known, a highly desirable feature of a rubberantioxidant is that it have a low volatility so. that it remains admixedwith the rubber during vulcanization and related process steps.

The present invention will be still further apparent from the followingspecific examples wherein all parts and percentages are by weight.

Example 1 To a synthetic rubber master batch comprising 100 parts ofSB-R rubber having an average molecular weight of 60,000, 50 parts ofmixed zinc propionate-ste-arate, 50 parts of carbon black, parts of roadtar, 2 parts of sulfur and 1.5 parts of mercapto-benzothiazole isincorporated 1.5 parts of 4,4-dithiobis-(2,6-di-tert-butylphenol). Thisbatch is then cured for 60 minutes at 45 p.s.i. of steam pressure.

Example 2 Two parts of 4,4-trithiobis-(2,6-di-tert-butylphenol) isincorporated in 100 parts of raw butyl rubber prepared by thecopolymerization of 90 percent of isobutylene and percent of isoprene.

Example 3 To 200 parts of raw butyl rubber prepared by copolymerizationof 95 percent of isobutylene and 5 percent of but-adiene is added 1.5parts of 4,4-trithiobis- 2,6-diisopropylphenol) Example 4 To a masterbatch of GR-N synthetic rubber comprising 100 parts of GR-N rubber, 5percent of zinc stearate, 50 parts of carbon black, 5 parts of road tar,2 parts of sulfur and 2 parts of mercaptobenzothiazole is added 5percent based on the weight of the batch of 4,4-dit-hiobis-2-tert-butyl-6-isopropylphenol) 4 Example 5 To a natural rubber (Hevea)is added 0.1 percent of 4,4-trithiobis- (2-ethoxy-6-sec-butylphenol)Example 6 Example 7 Three percent of 4,4 trithiobis (2,6diisopropylphenol) emulsified in sodium oleate is added to arubber-like, copolymer of butadiene-1,3 and styrene containing 25percent of combined styrene.

Example 8 A rubber stock is compounded from 100 parts of smoked s'heetrubber, parts of zinc oxide, 20 parts of lithopone, 2 parts of sulfur,0.7 part of diphenyl guanidine phthalate, 0.8 parts of benzoylthiobenzothiazole, 0.2 part of paraflin and 2 parts of4,4-dithiobis-(2-isopropyl-6-sec-butylphenol). The stock so compoundedis cured by heating for 45 minutes at 126 C. in a press.

Each of the above illustrated rubber compositions of this inventionpossesses greatly improved resistance against oxidative deterioration ascompared with the corresponding rubber compositions which are devoid ofan antioxidant. Moreover, the light-colored stocks of the above examplesexhibit virtually no discoloration or staining characteristics even whensubjected to severe weathering conditions and the like. The methods offormulating the improved rubber compositions of this invention will nowbe clearly apparent to those skilled in the art.

To illustrate the enhanced oxygen resistance of the rubber compositionsof this invention and their excellent non-staining and non-discolorationcharacteristics, a light-colored stock is selected for test. This stockhad the following composition:

Parts by weight Pale crepe rubber 100.00 Zinc oxide filler 50.00Titanium dioxide 25.00 Stearic acid 2.00 Ultramarine blue 0.12 Sulfur3.00 Meroaptobenzothiaz-ole 1.00

To the above base formula is added one part by weight of4,4-dithiobis-(2,6-di-tert-butylphenol), and individual samples arecured for 20, 30, 45 and 60 minutes at 274 C. using perfectly cleanmolds with no mold lubricant.

Another set of samples of the same base formula which do not contain anantioxidant are cured under the same conditions.

To demonstrate the protection afforded to the rubber by the practice ofthis invention, weighed samples, with and without inhibitor, aresubjected to accelerated aging. The aging is accomplished by conductingthe procedure of ASTM Designation: D-572-52, described in the ASTMStandards for 1952, Part 6, for a period of 168 hours at a temperatureof C. with an initial oxygen pressure in the test bomb of 300 p.s.i.g.

Measurements are made of the increase in weight of the test specimenswhich occurs during the accelerated aging. This is a direct measure ofthe oxygen up-take I of the samples and provides another criterion ofthe effectiveness of an inhibitor in suppressing oxidative deteriorationof the rubber. Thus, the larger the weight increase, the greater is thedeterioration and the less effective is the inhibitor.

In all the above tests, the composition compounded with4,4'-dithiobis-(2,6-di-tert-butylphenol) gives results which show thisadditive to be an excellent antioxidant.

The amount of stabilizer employed in the rubber compositions of thisinvention varies from about 0.01 to about 5 percent by weight based onthe weight of the rubber. The amount used depends somewhat upon thenature of the rubber being protected and the conditions of service to beencountered. Thus, in the stabilization of natural and synthetic rubberto be used in the manufacture of tires which are normally subjected toexposure to the elements, as well as to the action of sunlight,frictional heat, stress, and the like, the use of relatively highconcentrations of this inhibitor is advantageous. On the other hand,when the article of manufacture is not to be subjected to such severeconditions, relatively low concentrations can be successfully utilized.Generally speaking, amounts ranging from about 0.1 to about 3 percent byweight give uniformly satisfactory results.

Other rubbers and elastomers which can be preserved according to thisinvention are the rubbery polymerizates of isoprene, butadiene-1,3,piperylene; also the rubbery copolymer of conjugated dienes With one ormore polymerizable monoolefinic compounds which have the capability offorming rubber copolymers with butadiene-1,3, outstanding examples ofsuch monoolefinic compounds being those having the group CH C,exemplified by styrene. Examples of such monoolefins are styrene, vinylnaphthalene, alpha methyl styrene, para-chlorostyrene, dichlorostyrene,acrylic acid, methyl acrylate, methyl methacrylate, methacrylonitrile,methacrylamine, methyl vinyl ether, methyl vinyl ketone, vinylidinechloride, vinyl carbazole, vinyl pyridines, alkyl-substituted vinylpyridines, etc. In fact, excellent stabilization is achieved byincorporating a compound of this invention in any of the well-knownelastomers which are normally susceptible to deterioration in thepresence of air, such as elastoprenes, elastolenes, elastothiomers, andelastoplastics.

The novel compounds of this invention are also effective antioxidantadditives for saturated hydrocarbon synthetic polymers. Thus, anembodiment of this invention is a novel composition of matter comprisinga saturated hydrocarbon synthetic polymer derived from polymerization ofan aliphatic monoolefin hydrocarbon compound having up to 5 carbon atomsand a small antioxidant quantity, up to 5 percent, of a compound of thisinvention.

The saturated hydrocarbon synthetic polymer which is greatly enhanced byoxidative stability by the practice of this invention, includes polymersobtained from the polymerization of a hydrocarbon monoolefin having upto 5 carbon atoms. Examples of such monomers include ethylene,propylene, butylene and isobutylene. Thus, the polymers are homopolymersand copolymers of ethylene, propylene, butylene, isobutylene and thevarious pentenes.

A particularly preferred embodiment of this invention is polyethylenecontaining a small antioxidant quantity up to about 5 percent of4,4'-trithiobis-(2,6-di-tert-butylphenol).

Polyethylene is a hydrocarbon polymer derived from the polymerization ofethylene. This polymerization can be accomplished by a great variety ofmethods which leadto products of diverse properties. Polyethylene of anynature may advantageously be utilized for preparing compositionsaccording to the present invention. The polymers of ethylene which areemployed may, for example, be similar to those which may be obtained bypolymerizing ethylene in a basic aqueous medium and in the presence ofpolymerization favoring quantities of oxygen 6. under relatively highpressures in excess of 500 or 1,000 atmospheres at temperatures between150 and 275 C. Or, if desired, they may be similar to the essentiallylinear and unbranched polymers ordinarily having greater molecularweights which may be obtained under relatively low pressures of 1 toatmospheres using such catalysts to polymerize the ethylene as mixturesof strong reducing agents and compounds of group IVB, VB and VIB metalsof the Period System; chromium oxide on silicated alumina; hexavalentmolybdenum compounds; and charcoal supported nickel-cobalt. Thepolyethylene which results from these various polymerization processesmay have a molecular weight in the range from 1300 to over 1,000,000depending on the particular conditions of polymerization employed.

There are several methods available for preparing the inhibitedhydrocarbon polymer compositions of this invention. Thus, the blendingof the antioxidant of this invention with a polymer such as, forexample, polyethylene, may be carried out on open rolls, on internalmixers or may be accomplished by mixing with extrusion. It is alsopossible to prepare concentrated batches of the polymer containingexcessive amounts of the additive and then mix the concentrate withadditional polymer to prepare a composition of this invention. Thepreferred method of compounding the polymers is by milling on heatedopen rolls at slightly elevated temperatures by methods wellknown to theart. The temperature range employed is sometimes critical as certainpolyethylenes will not melt at low temperatures and tend to stick to therolls at high temperatures. The antioxidant may be initially mixed withthe polymer in the dried state or it may be first dissolved in asuitable solvent, then sprayed on the polymer and milled in.

The benefits derived from the practice of this invention aredemonstrated by comparative oxidation tests of un inhibited polyethyleneand polyethylene containing an antioxidant of this invention. Thesetests are conducted as follows: The selected amount of antioxidant isblended with the polyethylene by milling a weighed quantity of plasticpellets on a warm roll-mill. The weighed quantity of antioxidant isadded to the mill after the polyethylene has been pre-milled for a shortperiod of time. The plastic containing the antioxidant is then added inweighed quantity to a standard size vessel and melted to give a surfaceof reproducible size. The vessel is then inserted into a chamber whichmay be sealed and which is connected to a capillary tube leading to agas buret and leveling bulb. The apparatus is flushed with oxygen atroom temperature, sealed, and the temperature is raised to C. The oxygenpressure is maintained at one atmosphere by means of a leveling bulb.The oxygen uptake at the elevated temperature is recorded until sharpincrease in the oxygen uptake occurs. This procedure has been adoptedsince it has been found that many compounds may inhibit the oxidationfor a'certain induction period after which time a very sharp increase inthe rate of oxygen uptake occurs. This increase indicates that theantioxidant has been exhausted. In tests of this nature it is found thatthe compounds of this invention greatly increase the induction period ofthe polyethylene.

Example of the hydrocarbon polymer compositions of this inventionprepared as described above follow. All parts and percentages are byweight in these examples.

Example 9 To 1,000 parts of a solid polypropylene polymer having adensity of 0.905 and a Rockwell hardness greater than 85 and which isisotactic is added and blended to 5 parts of4,4'-trithiobis-(2-,6-di-tert-butylphenol).

Example 10 To an isotactic polypropylene having a tensile strengthgreater than 4300 psi. and a compressive strength of about 9,000 psi. isadded sufiicient 4,4'dithiobis-(2,6-

di-tert-butylphenol) to give a composition containing 0.5 percent of thecompound.

Example 11 To a wax-like polypropylene having a melting point above 130C. and a molecular weight of about 4,000, a density of 0.913 is added0.01 percent of 4,4-trithiobis- (Z-methoxy-6-isopropylphenol) Theantioxidant is added to the polypropylene in the molten state and themixture is allowed to solidify into the desired shape. A polypropyleneproduct of outstanding oxidative stability results.

Example 12 To 1,000 parts of polyethylene produced by oxygen catalyzedreaction under a pressure of 20,000 atmospheres and having an averagemolecular weight of 40,000 is added and mixed 2 parts of4,4'-dithiobis-2-ethoxy-6- isopropylphenol).

Example 13 To 100 parts of polyisobutylene having an average molecularweight of 100,000 is added 0.5 part of 4,4-trithiobis-2-iso-propyl-6-tert-butylphenol).

Example 14 To a master batch of high molecular weight polyethylenehaving an average molecular weight of about 1,000,000, a tensilestrength of 6,700 p.s.i., a Shore D hardness of 74 and a softeningtemperature under low load of 150 C. is added percent of4,4-dithiobis-(2, 6-di-sec-butylphenol).

Example 15 A linear polyethylene having a high degree of crystallinityup to 93 percent and below one ethyl branched chain hundred carbonatoms, a density of about 0.96 gram per milliliter and which has about1.5 double bonds per 100 carbon atoms is treated with 50x roentgens offl-radiation. To the thus irradiated polymer is added 0.005 percent of4,4'-trihiobis-(2,6-di-tert-butylphenol).

Example 16 To a polyethylene having an average molecular weight of 1500,a melting point of 8890 C. and a specific gravity of 0.92 is added 1percent of 4,4'-dithiobis- (2,6-di-tert-butylphenol). After milling inthe antioxidant an extremely oxidation resistant product results.

. Example 17 Two parts of 4,4-trithiobis-(2,6-diisopropylphenol) areadded with milling to 100 parts of a low density polyethylene preparedby high pressure polymerization and which has an average molecularweight of 18,000 to 20,000. The resulting product is vastly improved inits oxidative stability.

Example 18 To 10,000 parts of a polyethylene having an average molecularweight of about 100,000 and which has a tensile strength of 5400 p.s.i.,a Shore D hardness of 70 and a softening temperature of 130 C. under lowload is added 10 parts of 4,4'-trithiobis-(2,G-di-tert-butylphenol), toprepare a composition of outstanding oxidative stability.

Example 19 To the polyethylene in Example is added 0.05 percent of4,4'-dithiobis-(2,6-di-tert-b utylphenol). sulting composition hasimproved antioxidant characteristics.

Example 20 To a polyisobutylene polymer having an average molecularweight of 35,000 is added suflicient4,4-'dithiobis-(2-tert-butoxy-6-tert-butylphenol) to give a compositioncontaining 0.03 percent of the antioxidant. The

The recomposition has improved antioxidant properties due to thepresence of the additive.

In addition to the antioxidant of this invention the saturatedhydrocarbon polymers may contain other compounding and coloringadditives including minor proportions of carbon black, elastomers,polyvinyl compounds, carboxylic acid esters, unreaaldehyde condensationproducts, flame retarding agents such as antimony trioxide andchlorinated hydrocarbons and various pigment compositions designed toimpart color to the finished product.

In general, the amount of antioxidant employed in the hydrocarbonpolymers of this invention varies from about 0.001 percent to about 2percent or more. Most polymers are adequately protectedwithconcentrations ranging from 0.01 to about 1 percent.

The following examples illustrate various other embodiments of thisinvention. The physical character istics of the illustrative oils usedin Examples 21-26 are shown in Table I.

TABLE I.PROPERTIES OF REPRESENTATIVE PETROLEUM HYDROCARBON OILS Oil A BC D E F Gravity at 60 API 30.3 30.5 28. 8 31. 1 20. 5 3110 Viscosity,Saybolt:

Seconds at F 178. 8 373.8 309. 8 169.0 249. 4 335. 4

Seconds at 210 F 52.0 58. 4 63.8 51. 5 45. 7 68. 4 Viscosity Index 154.2 107. 4 141. 9 157. 8 35. 8 144. 4 Pour Point 30 +10 20 15 0 FlashPoint 410 4 305 385 Sulfur, Percent 0.2 0.3 0.3 0.3 0.3 0.1

Example 21 To 100,000 parts of Oil A is added with stirring 12 parts(0.012 percent) of 4,4-dithiobis-(2,6-di-tert-butylphenol). Theresulting oil is found to possess improved resistance to oxidativedeterioration.

Example 22 To 100,000 parts of Oil B is added 2,000 parts (2 percent) of4,4'-trithiobis-(2-methoxy-6-tert-butylphenol). On agitating thismixture, a homogeneous solution results and the resulting oilcomposition possesses enhanced oxidation resistance.

Example 23 With 100,000 parts of Oil C is blended 50 parts (0.05percent) of 4,4-trithiobis-(2,6-di-tert-butylphenol). The resulting oilpossesses enhanced resistance against oxidative deterioration.

Example 24 To 100,000 parts of Oil D is added 100 parts (0.1 percent) of4,4'-dithiobis-(2-tert-butoxy-6-tert-butylphenol). The resulting oil isfound to possess enhanced resistance against oxidative deterioration.

Example 25 With 100,000 parts of Oil E is blended 5 parts (0.005percent) of 4,4'-trithiobis-(2-isopropoxy-6-tert-butylphe- 1101). Aftermixing the resulting oil possesses enhanced resistance to oxidation.

Example 26 To 100,000 parts of Oil F is added parts (0.15 percent) of4,4'-dithiobis-(2,6-di-tert-butylphenol). The resulting oil possessesenhanced resistance against oxidative deterioration.

Example 27 With 100,000 parts of di-(sec-amyl) sebacate having aviscosity at 210 F. of 33.8 Saybolt Universal seconds (SUS), a viscosityindex of 133 and a molecular weight of 342.5 is blended 100 parts (0.1percent) of 4,4'-trithiobis-(2-ethoxy-6-sec-butylphenol). The resultingdi- .7tt.l.ttwuumlllhllllhtllllllll ester lubricant possesses greatlyenhanced resistance against oxidative deterioration.

Example 28 Example 29 To 100,000 parts of di-(Z-ethylhexyl) adipatehaving a viscosity at 210 F. of 34.2 SUS, a viscosity index of 121 and amolecular weight of 370.6 is added 2,000 parts (2 percent) of4,4'-trithiobis-(2,6-di-tert-butylphenol). After mixing, the resultantdiester lubricant possesses outstanding resistance against oxidativedeterioration.

Most lubricant compositions are adequately protected by the inclusion offrom 0.01 to about 2 percent of an antioxidant of this invention.However, in some cases, it is desirable to add amounts outside thisrange.

The compounds of this invention effectively stabilize such lubricatingand industrial oils as crankcase lubrieating oils, transformer oils,turbine oils, transmission fluids, cutting oils, gear oils, industrialoils, mineral white oils, glass annealing oils, oils thickened withsoaps and inorganic thickening agents (grease), and, in general, engineand industrial oils which are derived from crude petroleum and arenormally susceptible to deterioration in the presence of air,particularly at elevated temperatures and most particularly in thepresence of iron oxide. Furthermore, the novel compounds of thisinvention very effectively enhance the oxidation resistance of suchdiester oils as diethyl oxalate; di-sec-butyl malonate; di-(2-hexyl)succinate; di-(isoheptyl) pimelate; di- .(3-decyl) suberate; di-sec-amylglutarate; di-(isobutyl) glutarate; di-2-ethylbutyl) glutarate;di-(Z-ethylhexyl) lglutarate; di-sec-amyl adipate; di-(3-methylbutyl)adipate; diethyl adipate; di-Z-ethylhexyl adipate; di-sec-amyl azelate;di-(isobutyl) azelate; di- (2ethylbutyl) azelate; di- (Z-ethylhexyl)azelate; di-sec-amyl sebacate; di-sec-butyl sebacate; di-(2-ethylhexyl)sebacate; the glutarates, adipates, azelates and sebacates of branchedchain secondary alcohols, such as undecanol, tetradecanol, etc., and, ingeneral, diesters of the type described in the literature as useful forsynthetic lubricant purposes.

In the lubricant compositions of this invention effec tive use can bemade of other additives which are known to the art, such as otherinhibitors, detergent-dispersants, pour point depressants, viscosityindex improvers, antifoam agents, rust inhibitors oiliness or filmstrength agents, dyes and the like. Of the inhibitors which can beefiectively used in combination with our inhibitors are sulfurized spermoil, sulfur-ized terpenes, sulfurized paraflin wax olefins, aromaticsulfides, alkyl phenol sulfides, lecithin, neutralized dithiophosphates,phosphorous pentasulfide-terpene reaction products, diphenylamine,phenylnap-hthyl amine, B-naphthol, pyrogallol, and the like. Typical ofthe detergent additives that can be used-in the compositions of thisinvention are metallic soaps of high molecular weight acids, such asaluminum naphthenates, calcium phenyl stearates, calcium alkylsal-icylates, alkaline earth metal petroleum sulfonates, alkaline earthmetal alkyl phenol sulfides (barium amyl phenol sulfide, calcium octylphenol disulfide, etc.), metal salts of wax-substituted phenolderatives, and the like. Of the viscosity index improvers and pour pointdepressants, effective use can be made of polymers of the esters ofmethacrylic acids, highly fatty alcohols and the corresponding polymersof esters of acrylic acid and higher fatty alcohols. These and otheradditives which can be employed in the compositions of this inventionwill now be well known to those skilled in the art.

10 Example 30 To 1,000 parts of gasoline having 44.0 percent paraffins,17.9 percent olefins and 38.1 percent aromatics, an initial evaporationtemperature of 94 F. and a final evaporation temperature of 119 F. isadded 10 parts of 4,4-trithiobis-(2,6-di-tert-butylphenol). The mixtureis agitated to dissolve the compound. The resulting fuel has anexcellent stability to oxidative deterioration.

Example 31 To 1,000 parts of commercially available diesel fuel havingan octane number of 51.7 and 50 percent evaporation temperature of 509F. is added 3 parts of 4,4- dithiobis-(2,6-di-tert-butylphenol). Theresulting fuel is stable to oxidative deterioration.

Example 32 To an antiknock fluid composition which is to be used as anadditive to gasoline and which contains 61.5 parts of tetraethyllead,17.9 parts of ethylene and 18.8 parts of ethylene dichloride is added,with agitation, 1.3 parts of 4,4'-trithiobis-(2-isopropyl-6-tertbutylphenol). The resulting composition is stable for long periods whenexposed to air.

Example 33 With 1,000 parts of melted lard is mixed one part (0.1percent) of 4,4-dithiobis-(2,6-di-tert-butylphenol). After cooling, thelard can be stored for long periods of time without the development ofrancidity.

Example 34 To 5,000 parts of olive oil is added one part of 4,4-trithiobis-(2,6-di-tert-butylphenol) and the mixture is agitated toproduce a homogeneous blend which is stable to oxidative deteriorationfor a long period.

Example 35 4,4'-dithiobis-(2,6-di-tert-butylphenol) was dissolved inpure white refined mineral oil to the extent that 1.O 10 moles per literof the phenol was present in the mineral oil. Ferric hexoate was alsoadded to the mineral oil. The concentration of the iron salt wasadjusted to 0.05 percent based on Fe O One milliliter of the resultingcomposition was charged to an apparatus for measuring the oxidativestability of the mineral oil.. The apparatus consists of a glass vesselhaving a 12 milliliter capacity and an inlet tube which can be connectedto a mercury manometer. The vessel is flushed withoxygen at atmosphericpressure and then connected to the mercury manometer. It is thenimmersed in a constant temperature bath at 150 C. whereupon the oxygenpressure rise is indicated on the manometer. 'I'he manometer is observeduntil a rapid pressure drop in the vessel occurs. The time fromimmersion to initiation of the pressure drop is referred to as theinduction period of the mineral oil. When mineral oil containing theiron hexoate is subjected to this oxidative test, a pressure drop in themanometer is observed in from 2 to 3 minutes, showing that the mineraloil is unstable to oxidative deterioration at 150 C. However, when thecomposition containing 10x10 moles per liter of 4,4-dithiobis-(2,6-di-tert-butylphenol) is tested in this fashion, nopressure drop is observed in the manometer until after 125 minutes.Thus, the mineral oil has been improved by a factor of about 50 againstoxidative deterioration by the presence of this small amount of4,4'-dithiobis- 2,6-di-tert-butylphenol) Example 36 The procedure of theabove example is followed employing 1.0 10 moles per liter of4,4'-trithio bis-(2,6- di-tert-butylphenol). In this instance there wasno pressure drop in the manometer until after 216 minutes, indicatingthat the oil was improved by a factor of about against oxidation.

The compounds of this invention may be prepared by a process whichconsists of reacting the parent phenolic compound (for example,2,6-di-tert-butylphenol) with a sulfur chloride. Either sulfurmonochloride, S Cl or sulfur dichloride, SCl may be used.

The temperatures employed in this process vary over a wide range.However, low reaction temperatures reduce the yield of compounds of thisinvention in favor of the monothiobis compounds. On the other hand,excessively high reaction temperatures cause disassociation of sulfurdichloride and lead to excessive chlorination of the starting phenol. Ingeneral, temperatures from about 15 to 70 may be employed with:bestresults being obtained from about 25 to about 50.

It is convenient to conduct the preparation in suitable solvent. Thesolvents applicable are now boiling hydrocarbons, halogenatedhydrocarbons and inert aromatic compounds such as nitro benzene.Examples of suitable solvents include carbon tetrachloride, chloroform,N- hexane, 2,4-dibromopentane, low boiling petroleum ether and the like.

Another method which may be employed consists of first reacting thestarting phenol withsulfur monochloride or sulfur dichloride at lowtemperatures between 5 and 35 C. and then treating the reaction productwith elemental sulfur at elevated temperatures. In this manner, both the4,4'-dithiobis and 4,4-trithiobis phenols may be prepared.

The following examples, in which all parts are by weight, areillustrative of the methods for preparing the compounds of thisinvention.

Example 37 A solution of 206 parts of 2,6-di-tert-butylphenol in about300 parts of ethylene dichloride is stirred at to under a nitrogenblanket. 62 parts of sulfur dichloride in about 100 parts of ethylenedichloride is slowly added. After addition of the sulfur dichloride, thereaction mixture is warmed to and maintained at C. for about 6 hours andthen after prolonged standing, to for a short period of time. Thereaction is complete at 35 C. as evidenced by the fact that warming tocauses no further evolution of hydrogen chloride. The. reaction mixtureis cooled and filtered and the residue washed with ethylene dichloride.The filtrate and ethylene dichloride wash are combined and washed withwater,

then washed with dilute sodium bicarbonate followed by a second waterwash. The ethylene dichloride solution is then dried and stripped of thesolvent at reduced pressure to give an excellent yield of4,4'-dithiobis-(2,6-ditert-butylphenol). This compound melts at 144147C. and analyzes for the calculated sulfur content, 13.5 percent.

Example 38 A solution of 227 parts of distilled SCl and about 240 partsof petroleum ether (boiling point 36.5-38 C.) was added slowly withstirring to a solution of 712 parts of 2,6-diisopropylphenolin 400 partsof the petroleum ether. External cooling was applied to maintain thereaction mixture at about 17 C. About /2 the sulfur dichloride solutionwas added over a 30 minute period during which time the evolution of HClgas indicated that the reaction was proceeding. After M2 the sulfurdichloride had been added, the solution was refluxed at 38 C. for /2hour. The remaining sulfur dichloride was then slowly added over a /2hour period while the temperature was maintained between 18 and 24 C.The mixture was again refluxed for 30 minutes and then treated withactivated charcoal, filtered and additional petroleum ether added.

'The product 4,4'-thiobis-(2,6-diisopropylphenol) is further reactedwith an excess of sulfur to prepare 4,4'-trithiobis-2,6-diisopropylphen0l 1 2 Example 39 360 parts of freshly redistilledortho-tert-butyl guaiacol with a boiling point of l17121 C. at 6.5millimeters was diluted with low boiling petroleum ether in a stirredreaction vessel and 103 parts of sulfur dichloride also diluted with lowboiling petroleum ether, was slowly added at 10-15 C. After addition ofthe sulfur dichloride was complete, the reaction mixture was warmed to30 C. and left to stand .at room temperature for about two days. Thereaction mixture was then washed first with water, then with aqueoussodium bicarbonate and again with water, and then dried over calciumsulfate.

millimeter pressure, leaving 230 parts residue of 4,4'-dithiobis-2-methoxy-6-tert-butylphenol) This compound, on analysis, was shown tocontain 15.7 percent sulfur. The calculated content of 4,4'-d-ithiobis-(2-methoxy-6-tert-butylphenol) is about 15.2 percent sulfur.

In a similar manner other 4,4'-diand trithiobis-(2- alkoxy-6-branchedalkylphenol) compounds of this invention are prepared by reacting sulfurdichloride with 2-alkoxy-6-branched alkylphenol. Thus, 4,4,'-dithiobis-(2-tert-butoxy-6-isopropylphenol) is prepared by reacting2-tert-butoxy-6-isopropylphenol with sulfur dichloride.

Example 40 To a glass reaction vessel was charged 4,000 parts of carbontetrachloride, 444 parts of carbon disulfide and 515 parts of 2,6-di-tert-butylphenol. The mixture was cooled to -15 C. and 129 parts of sulfurdichloride was slowly added thereto over a 1 /2 hours period. Themixture was then stirred at room temperature for 1 /2 hours and thenheated to 50 C. for 15 minutes. The volatiles were then removed underreduced pressure producing a mixture of solid and oil which wasdissolved in ether and washed with aqueous sodium carbonate, water andthen dried over magnesium sulfate. 4,4'-dithiobis-(2,6-di-tert-butylphenol) is recovered from this reaction mixture.

Example 41 A solution of 34 parts of freshly distilled sul-furdichloride in about 25 parts of petroleum ether was slowly added withstirring to a solution of 123.6 parts of 2,6-ditert-butylphenol in 60parts of petroleum ether. Onehalf of the sulfur dichloride was addedslowly at 20 to 25 C. and the mixture was heated to reflux, then cooledto 25 C. and the remaining sulfur dichloride was slowly added.Thereafter the mixture was kept at reflux for 99 hours. The solvent andvolatiles were stripped under vacuum. Thereafter the resultingbrownish-black oil was subjected to distillation and the residue wasfractionally crystallized from methanol. After recovery of the fractionof crystals, the methanol solution was allowed to stand for an extendedperiod of time during which 2 parts of material crystallized.Recrystallization of this material from percent methanol gave yellowcrystals of 4,4- trithio bis-(2,6-di-tert-butylphenol) having a meltingpoint of 129-130 C. The compound, on analysis, was shown to contain 19.0percent sulfur. The calculated content for4,4-trithiobis-(2,6-di-tert-butylphenol) is 18.97 percent sulfur.

Example 42 2,6-di-tert-butylphenol (103 parts) is dissolved in 189 partsof ethylene dichloride. Sulfur monochloride (40.5 parts) in 63 parts ofethylene dichloride is added over a /2 hour period while the temperatureis maintained at 3538 C. with agitation. After the addition is completethe temperature is maintained at 35 for an additional hour. The reactionmixture is poured into stirred ice water. The water phase is separatedand discarded. The water insolubles are washed once with water, oncewith 5 percent sodium bicarbonate and twice more with,wl-mllllllllitllil After drying, the solvent was removed in vacuo at 95C. and 0.1

water. The organic phase is then dried and the solvent is removed bydistillation under vacuum. After the solvent is removed the distillationis continued and at 0.2 millimeter pressure at 90, a solid separateswhich is a chlorinated product. After this solid is removed theremaining residue is dissolved in a mixture of methanol and water andfractionally crystallized. A yellow crystalline precipitate is separatedfrom the solution and washed with cold dilute methanol and dried. Atotal of 118 parts of 4,4'-trithiobis-(2,6-di-tert-butylphenol) isobtained by the reaction. 4,4'-dithiobis-(2,6-di-tertbutylphenol) isalso obtained.

Example 43 In a reaction vessel equipped with heating means, coolingmeans, means for agitation and means for charging and discharging liquidand solid reactants was placed 412 parts of 2,6-di-tert-butylphenoldissolved in 1200 parts of nitrobenzene. The solution was agitated at1520 C. and 103 parts of sulfur dichloride in 300 parts of nitrob-enzenewere slowly added over a 40 minute period. After addition of the sulfurdichloride was complete, agitation was continued until evolution ofhydrogen chloride ceased. The reaction temperature was then raised to 35for 30 minutes and then to-45 for an additional 10 minutes at whichpoint no more hydrogen chloride evolved at 45. The mixture was thenchilled in an ice bath and volatiles were subsequently removed. Thefinal distillation conditions were 0.1-0.01 milliliter of mercury atsteam bath temperature. After the removal of volatiles the residuecontained a yellow solid from which both 4,4- dithiobis-(2,6 ditert-butylphenol) and 4,4 trithiobis- (2,6-di-tert-butylphenol) wereisolated.

I claim:

1. Organic material normally tending to deteriorate in the presence ofair, oxygen or ozone protected against such deterioration by theinclusion therein of a small antioxidant quantity of a compound havingthe formula:

'14 wherein R is an alkyl group branched on the alpha carbon atom havingfrom 3 to 4 carbon atoms, inclusive, R is an alkyl group branched on thealpha carbon atom having from 3 to 4 carbon atoms inclusive, and x is aninteger from 2 to 3.

2. The composition of claim 1 wherein said organic material is asaturated hydrocarbon synthetic polymer derived from polymerization ofan aliphatic mono-olefin hydrocarbon compound having up to 4 carbonatoms.

3. The composition of claim 2 wherein said saturated hydrocarbonsynthetic polymer is polyethylene.

4. The composition of claim 1 wherein said organic material is rubber.

5. The composition of claim 4 wherein said rubber is sulfur vulcanizedrubber.

6. The composition of claim 1 wherein said organic material is alubricating oil selected from the group consisting of hydrocarbonlubricating oil and synthetic nonhydrocarbon lubricating oil.

References Cited by the Examiner UNITED STATES PATENTS DANIEL E. WYMAN,Primary Examiner.

ALPHONSO D. SULLIVAN, Examiner.

E. W. GOLDSTEIN, P. P. GARVIN,

Assistant Examiners.

1. ORGANIC MATERIAL NORMALLY TENDING TO DETERIORATE IN THE PRESENCE OFAIR, OXYGEN OR OZONE PROTECTED AGAINST SUCH DETERIORATION BY THEINCLUSION THEREIN OF A SMALL ANTIOXIDANT QUANTITY OF A COMPOUND HAVINGTHE FORMULA:
 6. THE COMPOSITION OF CLAIM 1 WHEREIN SAID ORGANIC MATERIALIS A LUBRICATING OIL SELECTED FROM THE GROUP CONSISTING OF HYDROCARBONLUBRICATING OIL AND SYNTHETIC NONHYDROCARBON LUBRICATING OIL.